NOVEL FUNCTIONALIZED ISOOLEFIN/PARA-ALKYLSTYRENE COPOLYMERS

Abstract: The present invention comprises a functionalized polymer of an isoolefin having from about 4 to about 7 carbon atoms and a para-alkylstyrene wherein the functionalized polymer comprises a para-alkylstyrene moiety represented by formula (I), wherein R and R1 are independently selected from the group consisting of hydrogen, alkyl and primary and secondary alkyl halides.

Description: NOVEL FUNCTIONALIZED ISOOLEFIN/ PARA-ALKYLSTYRENE COPOLYMERS FIELD OF THE INVENTION The present invention relates to novel functionalized isoolefin/para-al ylstyrene copolymers. BACKGROUND OF THE INVENTION: Polymer-polymer adhesion plays a significant role in deter¬ mining the physical properties such as the stress-strain properties of immiscible blends. Improved adhesion between ductile and brittle components, for example, improves the ultimate properties. The extent of local or even segmental diffusion of chains across the interface between the blend components critically affects the mechanical strength and integrity of the adhesive bonding. Low or nonexistent segmental diffusion is the direct result of polymer-polymer immiscibility leading to a nondiffuse interface and generally poor interfacial strength. Polymer-polymer adhesion increases markedly and blend properties improve when the polymer components are semicompati¬ ble. This suggests that the properties of strongly immiscible blends would be enhanced if the interfacial area could be strengthened. This is typically done via addition of interfacially active polymers such as graft or block copolymers. Basically, the compatibilizer has blocks or grafts that are miscible to their respective phases. The polymeric compatabilizer "spans" the interfacial region and thus results in improved adhesion with correspondingly improved mechanical properties. It is, therefore, important to synthesize block or graft copolymers that act as a compatibilizer for strongly phase separated blends, especially rubber-modified blends. It is an object of the present invention to provide novel functionalized isoolefin para-alkylstyrene copolymers that are partic¬ ularly suitable for use in forming graft copolymers that can act as compatibilizers for polymer blends. SUMMARY OF THE INVENTION Briefly stated, the present invention comprises a functionalized polymer of an isoolefin having from about 4 to about 7 carbon atoms and a para-alkylstyrene wherein the functionalized polymer comprises a para-alkylstyrene moiety represented by the formula: wherein R and Ri are independently selected from the group consisting of hydrogen, alkyl and primary and secondary alkyl halides. In a preferred embodiment of the present invention, the novel functionalized polymer has a number average molecular weight of at least about 25,000 and preferably at least about 30,000 to about lθ6 and a ratio of weight average molecular weight to number average molecular weight of less than about 6 and more preferably less than about 4 to 1.0. The novel compounds of the present invention are particular¬ ly suitable for grafting with polymers containing groups capable of reacting with the oxazoline group on the novel polymer. In a preferred embodiment of the present invention, the novel polymer has from 0.1 meq oxazoline functionality per 100 g polymer to about 100.0 meq oxazoline functionality per 100 g polymer. DETAILED DESCRIPTION OF THE INVENTION The functionalized polymer of the present invention includes an isoolefin having between 4 and 7 carbon atoms and a para- alkylstyrene in which the functionalized polymer includes para- alkylstyrene moieties represented by the formula: wherein R and Ri are independently selected from hydrogen, alkyl and primary, and secondary alkyl halides. A typical functionalized polymer of the present invention can be represented by the formula: wherein R and Ri are independently selected from hydrogen, alkyl, primary and secondary alkyl halides and in which the combination of a+b+c+d represents the impirical formula of a substantially random graft copolymer where a ranges from about 4 to 70,000; b from 0 to about 70,000; c from 0 to 70,000; and d from 1 to 70,000; and in which X represents a halogen. The novel polymers of the present invention are prepared by contacting a polymer of an isoolefin having 4 to 7 carbon atoms and a para-alkylstyrene, which polymer contains benzylic halide, with 2-(m-hydroxypheny1 )-2-oxazoline in the presence of a suitable catalyst for a time and temperature sufficient to form the novel functionalized polymer. Typically, the benzylic halide containing para-alkylstyrene units in the copolymer will have the formula: wherein R and R\ are independently selected from hydrogen, alkyl and primary and secondary alkyl halides and X is a halide, preferably bromide. Isoolefin para-alkylstyrene copolymers containing benzylic halide that are suitable in the practice of the present invention are United States Patent 5,162,445, which is incorporated herein by reference. In preparing the compounds of the present invention, the copolymer containing the benzylic halide and the oxazoline compound are contacted preferably in the presence of a catalyst, such as a t-butyl ammonium hydroxide at temperatures from about 20 β C to about 150 β C for a time sufficient to displace the halide from the benzylic group and form the oxazoline functionalized copolymer. Preferably, the contacting is conducted in a solvent such as chlorobenzene, toluene and dichlonethane. Generally, contacting is conducted for from about 1 to about 24 hours. An important feature of the functionalized polymers of the present invention is their reactivity. The oxazoline group is readily reactive with many functionalities in other polymers. For example, the oxazoline functionality is readily reactive with polymers contain¬ ing a pendant carboxylic acid group, such as a carboxylic acid, a carboxylic acid anhydride or a carboxylic acid halide group, thereby forming graft copolymers of improved mechanical properties. Particu¬ larly suitable compounds that are reactive with the oxazoline func¬ tionalized isoolefin para-styrene copolymer are polystyrene monocar- boxylic acid, polystyrene carboxylic acid anhydride and polystyrene carboxylic acid chloride. EXAMPLES Example 1 A mixture of 6g of 2-(m-hydroxylphenyl)-2-oxazoline and 24g of tetrabutyl ammonium hydroxide (50 wt.% in aqueous solution) was introduced into 200 mis of chlorobenzene which contained lOg of commercially available bromo-p-methylstyrene-isobutylene copolymer having 13.8 meq of the bromo-p-methyl styrene per 100 g of polymer. The mixture was kept at 55 β C with continuous stirring for 24 hours. The polymer was precipitated in 1600 ml isopropyl alcohol. The precipitate was dissolved in 300 is tetrahydrofuran and subsequently filtered through a diatamaceous earth filter aid. The filtrate was added to 800 mis of isopropyl alcohol to precipitate the functionalized polymer (I). The polymer (I) was dried in a vacuum oven at 40 * C. The yield was 92% based on recovered polymer. NMR analysis showed that benzylic bromides were absent and oxazoline peaks appeared at _=3.9 and 4.4 and the peak at 5=5.1 was assigned to the benzylic ether. Examples 2 to 4 The grafting of polystyrene onto the oxazoline functional¬ ized polymer (I) of Example 1 was conducted using polystyrene mono- carboxylic acid (PSCO2H), polystyrene carboxylic acid anhydride ((PSC02)0) and polystyrene carboxylic acid chloride (PSC0C1). The general scheme using the acid chloride is as follows: 1.6g poly¬ styrene monocarboxylic acid chloride (M n =13,000g/mole) in 10 ml anhydrous 1,2-dichlorobenzene was introduced in 10 ml anhydrous 1,2-dichlorobenzene solution containing l.Og of the oxazoline func¬ tionalized butyl rubber polymer (I) of Example 1 at 100 β C. The reaction proceeded for 5 hours. The reaction mixture was cooled and diluted with 20 ml of chloroform. The polymer was precipitated with methanol and unreacted polystyrene was extracted by boiling acetone for one hour. The extracted polymer (II) was dried in a vacuum oven at 50 β C for 48 hours. Yield was 2.0g. GPC, NMR and DSC analysis con¬ firmed complete reaction of the oxazoline moieties with polystyrene. The resulting graft copolymer (II) was molded at 140 β C at 20 tons pressure to obtain a pad. Tensile specimens were cut from the pad for mechanical property evaluation. Table 1 shows the properties (tensile measurements) of the grafted copolymer (II) compared to a physical mixture of bromo-p-methylstyrene-butylene copolymer (III) and polystyrene carboxylic acid (PSCO2H). The grafted copolymer is a thermoplastic elastomer with excellent properties. The unreacted mixture has poor properties due to poor interfacial characteristics. Table 1 Properties of Grafted Butyl Copolymer and its Physically Blended Counterpart Stress at Strain at Modulus Break Break Sample (PSIl (PSI) (%. II 153,100 2,491 13 Blend of III and PSCO2H 7,069 37 47

Claims: CLAIMS : 1. A functionalized polymer of an isoolefin having from about 4 to about 7 carbon atoms and a para-alkylstyrene in which functionalized polymer at least one para-alkylstyrene moiety has the formula: wherein R and ^ are independently selected from the group consisting of hydrogen, alkyl and primary and secondary alkyl halides. 2. The functionalized polymer of claim 1 wherein R and Ri are hydrogen. 3. The copolymer of claim 1 wherein the copolymer has a number average molecular weight of from about 25,000 to about 10*. 4. The polymer of claim 1 wherein the isoolefin has 4 carbon atoms. 5. A functionalized polymer represented by the formula: wherein R and Ri are independently selected from hydrogen, alkyl, primary and secondary alkyl halides and in which the combination of a+b+c+d represents the impirical formula of a substantially random graft copolymer where a ranges from about 4 to 70,000; b from 0 to about 70,000; c from 0 to 70,000; and d from 1 to 70,000; and in which X represents a halogen. 6. A method of forming an oxazoline functionalized polymer comprising: contacting a polymer of an isoolefin and a para-alkylstyrene containing benzylic halide with 2-(m-hydroxyphenyl)-2-oxazoline in the presence of a catalyst and at a temperature and for a time sufficient to functionalize the polymer with a pendant group containing oxazoline. 7. The method of claim 6 wherein the contacting is conduct¬ ed in a solvent and the catalyst is t-butyl ammonium hydroxide. 8. The method of claim 7 wherein the solvent is selected from the group consisting of chlorobenzene, toluene, and dichloroehtane. 9. The method of claim 8 wherein the temperature is in the range of from about 20 β C to about 150 β C. 10. The method of claim 9 wherein the contacting is from about 1 to about 24 hours.

Inventors: HSEIH DONG T, PEIFFER DENNIS G, WANG HSIEN C, HSEIH, DONG, T., PEIFFER, DENNIS, G., WANG, HSIEN, C.
Applicants: EXXON RESEARCH ENGINEERING CO, EXXON RESEARCH & ENGINEERING COMPANY
Application year: 1994
Main classification: C08F226
IPC codes: C08F8, C08F10, C08F12, C08F210, C08F212